http://www.w3.org/Bugs/Public/show_bug.cgi?id=2112
Summary: R-123: A question about redefining redefines
Product: XML Schema
Version: 1.0
Platform: All
OS/Version: All
Status: NEW
Severity: normal
Priority: P2
Component: XSD Part 1: Structures
AssignedTo: ht@w3.org
ReportedBy: sandygao@ca.ibm.com
QAContact: www-xml-schema-comments@w3.org
There are situations in which the redefinition of a type, and the subsequent
redefinition of the redefined type, are desirable. One such case is where a
schema user would like to extend a type, not just from the original source but
based on the extension of another schema user's extension (Company C extends
type T from Company B, who picked it up from Company A and redefined it).
It appears that this is discouraged in the Rec. From 4.2.2:
"In all cases there must be a top-level definition item of the appropriate name
and kind in the redefined schema document.
NOTE: The above is carefully worded so that multiple equivalent redefining of
the same schema document will not constitute a violation of clause 2 of Schema
Properties Correct (3.15.6) , but applications are allowed, indeed encouraged,
to avoid redefining the same schema document in the same way more than once to
forestall the necessity of establishing identity component by component
(although this will have to be done for the individual redefinitions
themselves)."
Some validators require that the redefined schema contain a type definition for
a type that is to be redefined - that a redefinition is not sufficient. So it
is not possible to redefine a redefined type. So the question is, is this
something that is likely to change, or will validators vary on whether or not
they support cascading redefines?